Ball pen



FIG. 1 is a front elevation view of a ball pen showing my new design;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a left elevation view thereof;

FIG. 4 is a right elevation view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a top plan view thereof. 

CLAIM The ornamental design for a ball pen, as shown and described. 